1. Field of the Invention
The present invention relates to a coating apparatus for coating a substrate to be processed such as a semiconductor wafer or the like with a solution such as a resist solution, a developing solution, or the like and a mixing apparatus.
2. Description of the Related Art
In a photolithography process of the process of fabricating a semiconductor device, for example, resist coating processing of forming a resist film on the surface of a semiconductor wafer (hereinafter referred to as xe2x80x9ca waferxe2x80x9d) and developing processing for the resist-coated wafer are performed with exposure processing therebetween.
If notice is taken of the resist coating processing, a spin coating method or the like is frequently used as a method for uniformly coating the surface of the wafer with a resist solution. Resist coating by means of this spin coating method is performed as follows: the wafer is rotated while being vacuum-sucked by a spin chuck; the resist solution is dropped and supplied to the surface of the wafer from directly above the center of the rotation; and the resist solution is spread over the entire surface from the center of the wafer by centrifugal force. In a resist coating apparatus of this type, the thickness of a resist film can be controlled by the rotation speed of the spin chuck (wafer). Namely, with an increase in rotation speed, a thinner resist film can be obtained.
However, from the limits of the performance of the coating apparatus itself (the rotation speed of the spin chuck), a minimum value of a formable resist film thickness is restricted by itself. Therefore, whenever the thickness of a resist film is changed, resist solutions different in viscosity need to be prepared.
In order to cope with the aforesaid situation, an art in which a resist solution with a desired viscosity is supplied onto a wafer by controlling the mixing ratio of a resist solution to a thinner is described in Japanese Patent Laid-open No. Hei 10-242045 and Japanese Patent Laid-open No. Hei 10-272407.
In such a resist coating apparatus, however, the resist solution and the thinner have no compatibility, and hence mixing is insufficient in some cases. When the wafer is coated with a mixed solution in such an insufficient mixing state, ununiformity of resist film thickness within the surface of the wafer sometimes occurs.
An object of the present invention is to provide a coating apparatus for uniformly coating the surface of a substrate with a solution such as a resist solution which is applied to the substrate, and a mixing apparatus.
A coating apparatus of the present invention comprises: a holder for holding a substrate; a nozzle for supplying a mixed solution of a processing solution and a solvent to a surface of the substrate; a first pipe having a first inside diameter, for supplying the mixed solution to the nozzle; a second pipe having a second inside diameter, for supplying the processing solution to the first pipe; a third pipe having a third inside diameter, for supplying the solvent to the first pipe; a fourth pipe which has a fourth inside diameter smaller than all of the first inside diameter, the second inside diameter, and the third inside diameter, which is connected to the first pipe, the second pipe, and the third pipe, to which the processing solution and the solvent are supplied, and which supplies the mixed solution of the processing solution and the solvent to the first pipe.
A mixing apparatus of the present invention comprises: a first pipe having a first inside diameter, for discharging a mixed solution of a processing solution and a solvent; a second pipe having a second inside diameter, for supplying the processing solution to the first pipe; a third pipe having a third inside diameter, for supplying the solvent to the first pipe; a fourth pipe which has a fourth inside diameter smaller than all of the first inside diameter, the second inside diameter, and the third inside diameter, which is connected to the first pipe, the second pipe, and the third pipe, to which the processing solution and the solvent are supplied, and which supplies the mixed solution of the processing solution and the solvent to the first pipe.
According to the aforesaid structures of the present invention, the inside diameter of the junction pipe, for example, which is the fourth pipe is set to be smaller than the inside diameters of the other pipes, whereby the processing solution and the solvent can be mixed efficiently in the junction pipe. As a result, the mixed solution of the processing solution and the solvent to be supplied onto the substrate is mixed sufficiently, and hence the substrate can be coated with the mixed solution so that a uniform film thickness can be obtained within the surface of the substrate.